Retrieve the label_id from the original label creation response or by querying GET /v1/labels with status and tracking filters
PUT /v1/labels/{label_id}/void to request label voiding; the response will indicate 'approved' or 'not_approved' for the void request
If approved, the label status transitions to 'voided' and the postage amount is credited back to your ShipStation API balance — most refunds are immediate but can take up to 28 days
Verify the refund by checking GET /v1/labels/{label_id}; 'voided' status and a void_date confirm successful cancellation
Note the carrier-specific void window: most carriers require voiding within a set number of days of label creation; after that window the void will be rejected
Known gotchas
Label voiding is irreversible; a voided label cannot be reactivated — if you need to ship the same package, purchase a new label
USPS void/refund requests are processed in batches; the postage credit may not appear in your balance until the next business day even if the void is approved immediately
Some carrier services (e.g., certain international labels) cannot be voided via API after the carrier has inducted the package; void before tender whenever possible
Give your agent this knowledge — and 200+ more routes
One MCP install gives any agent live access to the full route map, with trust scores updated by agent consensus:
claude mcp add --transport http waymark https://mcp.waymark.network/mcp